This invention relates generally to filter assemblies and, more particularly, to various embodiments of a filter assembly configured for use with an air flow inducing device utilized in oxygen concentrators and other medical devices in the health care medical equipment industry.
Oxygen concentrators are commonly used in the care of respiratory patients, particularly, in the health care environment, to provide sufficiently high concentration of oxygen to the patient without having to use high pressure tanks or liquid oxygen. Oxygen concentrators utilize ambient atmospheric air as their source of oxygen in conjunction with a separation system such as one or more molecular sieve beds to separate oxygen from the other gases found in the air and to provide that oxygen in concentrated form to the patient. Atmospheric air typically includes approximately 80% nitrogen and 20% oxygen. In one form of separator, nitrogen is absorbed by an absorption system and is retained therein until subsequently purged. However, the concentrator and other medical devices tend to be subject to increased wear from atmospheric particles which can flow into the system, thereby decreasing the service life of the machinery, while increasing maintenance time and expense.
Typically, these issues are dealt with by a filter used in the in-feed air stream of the concentrator to filter particles and to protect the concentrator from particles and the patient from certain bacteria present in the atmosphere. HEPA filters are commonly used in these applications, and they are rated to remove 99.97% of the particles 0.3 μm or larger. These filters typically employ a large surface area (about 120 square inches of surface filtration area) and provide a long service life. Ambient air is drawn into an oxygen concentrator from the ambient environment. Such ambient air is then passed through a filter assembly to remove dust and other contaminants, and the filtered air is then pressurized by a compressor for introduction into the absorption system. Once the compressed air is introduced into the absorption system, the nitrogen is selectively absorbed and released to atmosphere leaving the residual oxygen available for patient use. The absorption system is then regenerated and made ready for the next cycle. Oxygen concentrators typically produce an oxygen concentration usually in the range of 90-95% by volume.
Use of an effective filtration system for separating contaminants from any gas is important for a multitude of reasons. Properly and effectively filtering the incoming ambient air before it is compressed and introduced into the absorption system of an oxygen concentrator is likewise important because effective filtration not only improves the overall efficiency of the oxygen concentrator but it also improves and increases the oxygen concentration provided to the patient. Poor filtration of the incoming air also subjects the oxygen concentrator and its associated compressor to increased wear from particles which enter the system thereby decreasing service life while increasing maintenance.
Filtration area is one factor for evaluating the performance of a filter apparatus. The size and overall configuration of the filter housing associated with a particular oxygen concentrator generally determine the maximum filtration area. However, the larger the filtration area with the same footprint of the filter housing is preferred for higher performance of the filter apparatus.
It is therefore desirable to provide a filter assembly which improves the air filtration performance to the absorption system of an oxygen concentrator or other compressor assembly, and which includes means for improving the filtration capacity and life of the filter assembly.
Prior art filters for use in an oxygen concentrator have been disclosed with features such as noise attenuation and easy replacement. For example, a filter with a single inlet is disclosed in Roberts et al, U.S. Pat. No. 6,702,880 entitled Inlet Silencer/Filter For An Oxygen Concentrator. The inlet silencer/filter for an oxygen concentrator includes a HEPA filter and an adjoining chamber for receiving air flow after passing through the HEPA filter. The chamber is defined on one face by the HEPA filter, and by sound absorbing padding on at least four (4) other faces. Air is directed from the HEPA filter, through the open chamber and then through the sound absorbing padding by a flow deflector plate. Air flows from here through air channels and into an open chamber leading to an outlet from the air silencer/filter. However, the amount of air passing through the single inlet associated with a filter member is limited.
Another filter is disclosed in Amann U.S. Pat. No. 7,141,101 entitled Filter Assembly With Noise Attenuation (Amann '101), which patent is owned by the present Assignee. Amann '101 discloses a filter assembly including a compartmented housing having an inlet opening, a single inlet chamber, an outlet opening, a filter member, and a plurality of noise attenuating members located therewithin. The configuration of the compartmented housing in conjunction with the positioning and location of the filter member and the noise attenuating members therewithin all contribute to dampen and dissipate sound waves generated within the housing due to air flow movement therethrough. However, the amount of air passing through the single inlet and inlet chamber associated with a filter member needs to be increased.
Amann U.S. Pat. No. 6,866,700 entitled Filter Housing Assembly For Use in Oxygen Concentrators and Other Compressors (Amann '700), which patent is likewise owned by the present Assignee, discloses a substantially frusto-conical shaped filter housing member having one or more inlet openings associated with a substantially closed dome shaped portion. Ambient air entering the one or more inlet openings flow through a single inlet chamber before passing through a substantially cylindrically shaped filter member and exiting through a single outlet opening. In this particular filter assembly, air travels from the outside of the filter member through the filter member to a central passageway extending through the interior portion of the filter member. Once the air has traveled to this interior passageway, it then flows through this interior passageway to the outlet opening for passage into a compressor assembly.
Accordingly, the present invention is directed to a filter assembly which overcomes one or more of the problems as set forth above.